U.S. patent application number 11/615027 was filed with the patent office on 2008-06-26 for detecting and reporting a picocell by a mobile station.
Invention is credited to Holger Claussen, Louis Gwyn Samuel, Lester Tse Wee Ho.
Application Number | 20080153533 11/615027 |
Document ID | / |
Family ID | 39204671 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080153533 |
Kind Code |
A1 |
Claussen; Holger ; et
al. |
June 26, 2008 |
DETECTING AND REPORTING A PICOCELL BY A MOBILE STATION
Abstract
An exemplary method of communicating includes storing a locating
neighbor list that corresponds to a mobile station being in a
communication range of a selected picocell. Upon receiving a
current neighbor list, a determination is made whether the current
neighbor list corresponds to the stored, locating neighbor list. If
there is sufficient correspondence, that indicates that the mobile
station is in a communication range of the picocell.
Inventors: |
Claussen; Holger; (Swindon,
GB) ; Wee Ho; Lester Tse; (Swindon, GB) ;
Samuel; Louis Gwyn; (Swindon, GB) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C./Alcatel-Lucent
400 W MAPLE RD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
39204671 |
Appl. No.: |
11/615027 |
Filed: |
December 22, 2006 |
Current U.S.
Class: |
455/522 |
Current CPC
Class: |
H04W 36/04 20130101;
H04W 36/32 20130101 |
Class at
Publication: |
455/522 |
International
Class: |
H04Q 7/22 20060101
H04Q007/22 |
Claims
1. A method of communicating, comprising the steps of: storing a
locating neighbor list corresponding to a mobile station being in a
communication range of a selected picocell; receiving a current
neighbor list; and determining whether the current neighbor list
corresponds to the locating neighbor list sufficiently to indicate
that the mobile station is in a communication range of the
picocell.
2. The method of claim 1, comprising establishing a communication
link with the selected picocell; determining a neighbor list
associated with a time of the established communication link; and
storing the locating neighbor list.
3. The method of claim 2, comprising registering the mobile station
with the picocell station.
4. The method of claim 1, comprising storing power measurements
associated with each of a plurality of cells in the locating
neighbor list; and determining current power measurements
associated with at least some of the plurality of cells that are
also in the current neighbor list; and determining whether the
current power measurements correspond to the stored power
measurements.
5. The method of claim 1, comprising performing measurements for a
cell code of the picocell responsive to determining that the
current neighbor list sufficiently corresponds to the locating
neighbor list.
6. The method of claim 5, comprising detecting the picocell; and
reporting the picocell to a base station currently serving the
mobile station.
7. The method of claim 6, comprising handing over from a currently
serving base station to the picocell responsive to sufficiently
detecting the picocell.
8. The method of claim 1, comprising determining an amount of
correspondence between the locating neighbor list and the current
neighbor list; and determining whether the amount of correspondence
exceeds a threshold as an indication that the mobile station is in
the communication range of the picocell.
9. The method of claim 1, comprising updating the stored determined
neighbor list upon establishing a new communication link with the
picocell.
10. The method of claim 1, comprising determining whether the
current neighbor list and the determined neighbor list are
identical.
11. A wireless communication mobile station device, comprising a
storage including a locating neighbor list corresponding to the
mobile station being in a communication range of a selected
picocell; a transceiver for receiving a current neighbor list; and
a detection module configured to determine whether the current
neighbor list corresponds to the locating neighbor list
sufficiently to indicate that the mobile station is in a
communication range of the picocell.
12. The device of claim 11, wherein the storage includes power
measurements associated with each of a plurality of cells in the
locating neighbor list; and the detection module is configured to
determine current power measurements associated with at least some
of the plurality of cells that are also in the current neighbor
list and to determine whether the current power measurements
correspond to the stored power measurements.
13. The device of claim 11, comprising a controller that is
configured to perform measurements for a cell code of the picocell
responsive to the detection module determining that the current
neighbor list sufficiently corresponds to the locating neighbor
list.
14. The device of claim 11, wherein the detection module is
configured to determine an amount of correspondence between the
locating neighbor list and the current neighbor list; and determine
whether the amount of correspondence exceeds a threshold as an
indication that the mobile station is in the communication range of
the picocell.
15. The device of claim 11, wherein the storage is configured to
update the stored determined neighbor list upon establishing a new
communication link with the picocell.
16. The device of claim 11, wherein the detection module is
configured to determine whether the current neighbor list and the
determined neighbor list are identical.
Description
1. FIELD OF THE INVENTION
[0001] This invention generally relates to communication. More
particularly, this invention relates to wireless communication.
2. DESCRIPTION OF THE RELATED ART
[0002] Wireless communication systems are well known and in
widespread use. Many systems are referred to as cellular systems
because of the way that wireless communication coverage is
designed. Base station transceivers are arranged to provide
wireless communication coverage over geographic areas surrounding
the base station. The geographic area is typically referred to as a
cell. Traditional base station transceivers provide relatively
large geographic coverage and the corresponding cells can be
referred to as macrocells.
[0003] It is possible to establish smaller-sized cells within a
macrocell. These are sometimes referred to as picocells. One
proposed way for establishing a picocell is to provide a picocell
base station unit that operates within a relatively limited range
within the coverage area of a macrocell. One example use of a
picocell base station unit is to provide wireless communication
coverage within a building, for example.
[0004] Various challenges are introduced by the possibility of
having multiple picocells within a macrocell. It is necessary to be
able to identify the picocells to facilitate accurate handovers
between the macrocell and a desired picocell, for example. With the
likely proliferation of many picocells, the task of identifying
each of them uniquely becomes daunting. Further, there must be some
mechanism for locating them for a possible handover.
[0005] It is necessary to generate a user-specific neighbor list
that includes candidate cells that a mobile station can consider.
In addition to the existing macrocells, it will become necessary to
include a user's home or work picocell, for example, within the
neighbor list. While creating a unique neighbor list for each user
that includes such a picocell is one possibility, there are
additional costs, complexity and signaling overheads on the network
side, which render such an approach undesirable. For example, one
radio network controller can control over 100 macrocell base
stations and there could be thousands of picocells within the
corresponding area. Providing unique neighbor lists for individual
mobiles places too high a burden on the network.
[0006] Additionally, it is not desirable for a mobile station to
continuously search for a home or work picocell because that wastes
energy and reduces mobile battery life. Further, the possibility of
scrambling code or PN offset re-use will result in incorrect
picocell identifications.
[0007] There is a need for an efficient arrangement for identifying
picocells in a manner that facilitates accurate handovers between a
macrocell and a desired picocell.
SUMMARY
[0008] An exemplary method of communicating includes storing a
locating neighbor list that corresponds to a mobile station being
in a communication range of a selected picocell. Upon receiving a
current neighbor list, a determination is made whether the current
neighbor list corresponds to the stored, locating neighbor list. If
there is sufficient correspondence, that indicates that the mobile
station is in a communication range of the picocell.
[0009] An exemplary wireless communication mobile station device
includes a storage having a locating neighbor list corresponding to
the mobile station being in a communication range of a selected
picocell. The mobile station device includes a transceiver for
receiving a current neighbor list. A detection module is configured
to determine whether the current neighbor list corresponds to the
locating neighbor list. When there is sufficient correspondence,
that indicates that the mobile station is in a communication range
of the picocell.
[0010] The various features and advantages of a disclosed example
will become apparent to those skilled in the art from the following
detailed description. The drawings that accompany the detailed
description can be briefly described as follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 schematically shows selected portions of a wireless
communication system that is useful with an embodiment of this
invention.
[0012] FIG. 2 schematically shows selected portions of an example
mobile station and schematically illustrates one example
approach.
DETAILED DESCRIPTION
[0013] FIG. 1 schematically illustrates selected portions of a
communication system 20. A base station 22 includes a base station
transceiver unit and appropriate radio communication equipment for
conducting wireless communications in a generally known manner. The
base station 22 establishes a wireless communication coverage area
24 that is referred to as a macrocell for purposes of discussion.
The geographic region of the macrocell 24 will depend on, in part,
the capabilities of the base station 22 and the surrounding
geography. There are known techniques for establishing a desired
macrocell coverage area.
[0014] Within the macrocell 24, a picocell base station unit
(PCBSU) 30 provides wireless communication coverage within a
picocell 32. As can be appreciated from the illustration, the size
of the coverage area of the picocell 32 is much smaller than that
of the macrocell 24. The illustration is not to scale but the point
is that the picocell coverage area of the picocell 32 is much
smaller than that of the macrocell 24. In one example, the picocell
32 corresponds to the user's home.
[0015] Another PCBSU 34 provides wireless coverage within a
picocell 36. Still another PCBSU 38 provides a picocell coverage
area 40.
[0016] It is possible for a mobile station 44 within the macrocell
24 to communicate with the macrocell by communicating with the base
station 22 in a known manner. When the mobile station 44 enters
into a picocell area where that mobile station is authorized for
communications within the picocell, it will be desirable to
handover from the macrocell 24 to the corresponding picocell. In
the illustrated example, the user of the mobile station 44 has
rights for using the communication capabilities of the PCBSU 30 for
communicating within the picocell 32.
[0017] The example mobile station 44 has a capability of detecting
and reporting the picocell 32 when it comes into a communication
range where the mobile station 44 can communicate with the PCBSU
30. FIG. 2 schematically shows selected portions of the mobile
station 44. A memory or storage 50 includes a locating neighbor
list 52 corresponding to at least one time when the mobile station
44 is in a communication range of the picocell 32. In one example,
the mobile station 44 stores the neighbor list from a time when
registering the mobile station 44 with the PCBSU 30. This may occur
during installation of the PCBSU or an initial use of the mobile
station 44 within the picocell 32, for example. In one example,
when the mobile station 44 has an active communication link with
the PCBSU 30, it stores the neighbor list available to it at that
time as the locating neighbor list 52.
[0018] The illustrated example storage 50 also includes a plurality
of measurements 54 that are made by the mobile station 44 at a time
associated with the stored locating neighbor list 52. For example,
the mobile station 44 makes a plurality of measurements from at
least some of the macrocell base stations or PCBSUs within the
locating neighbor list 52.
[0019] The locating neighbor list 52 will include at least a
plurality of macrocell base station identifiers. In some examples,
the locating neighbor list 52 will include PCBSUs associated with
nearby picocells, if appropriate. The mobile station 44 uses the
stored locating neighbor list 52 for purposes of determining when
it is nearby or within the picocell 32. The illustrated example
includes a PCBSU detection module 60 that utilizes the stored
locating neighbor list 52 for determining when the mobile station
44 is in a communication range of the picocell 32.
[0020] The mobile station 44 includes a transceiver portion 62 that
communicates with the serving macrocell base station 22. The
transceiver portion 62 receives a current neighbor list 64 provided
by a macrocell radio network controller, for example, as
schematically shown at 66. The PCBSU detection module 60 determines
whether the current neighbor list 64 corresponds to the stored
locating neighbor list 52. In one example, the PCBSU detection
module 60 determines whether there is an identical match between
the current neighbor list 64 and the locating neighbor list 52. In
another example, the PCBSU detection module 60 is capable of
determining a level of correspondence between the current neighbor
list 64 and the locating neighbor list 52. If the amount of
correspondence exceeds a threshold, the PCBSU detection module 60
determines that there is sufficient correspondence between the
current neighbor list 64 and the locating neighbor list 52 to
indicate that the mobile station 44 is likely within a
communication range of the picocell 32.
[0021] The amount of correspondence may be based upon various
factors such as a percentage of matching cell codes within the
neighbor lists 64 and 52. Another example technique for determining
an amount of correspondence between the neighbor lists 64 and 52
when they are not identical is to use measurements obtained by the
mobile station 44 associated with each list. The stored
measurements 54 may be compared to a set of current measurements 68
obtained by the mobile station 44 at the time of trying to
determine whether the current neighbor list 64 sufficiently
corresponds to the locating neighbor list 52. One example includes
determining whether at least a minimum percentage of the current
power measurements correspond to the stored measurements 54. If
there is sufficient correspondence between at least some of the
measurements and there is sufficient correspondence between the
members of the neighbor list 64 and the locating neighbor list 52,
the PCBSU detection module 60 in one example determines that the
mobile station 44 is within a communication range of the picocell
32. Another example technique includes using signal timing
information as a metric for determining correspondence or
similarity between the neighbor lists. Given this description,
those skilled in the art will be able to determine an appropriate
correlation technique and appropriate thresholds to meet the needs
of their particular situation.
[0022] An example that includes requiring some amount of
correlation between a current neighbor list and a stored locating
neighbor list provides an advantage over an arrangement where an
exact match between the neighbor lists is required. For example, if
there is a change in the macrocellular configuration over time,
that could cause a change in a current neighbor list such that it
would not match an out-dated, previously stored locating neighbor
list.
[0023] Once the mobile station 44 determines that there is
sufficient correspondence between the current neighbor list 64 and
the locating neighbor list 52, the mobile station 44 begins to
perform measurements for the PCBSU 30 cell code (e.g., UMTS
scrambling code or CDMA PN offset or an equivalent). In one
example, the mobile station 44 also begins to perform measurements
for neighboring PCBSUs to assist in identifying whether the mobile
station 44 is, in fact, in the vicinity of the picocell 32.
[0024] When the mobile station 44 detects the PCBSU 30 signal, it
reports the cell code of the PCBSU 30 back to the macrocell base
station 22 as schematically shown at 70. The PCBSU 30 is,
therefore, reported as part of the mobile station's detected set.
The radio network controller associated with the macrocell base
station 22 responsively includes the PCBSU 30 in the measured set
and requests measurements from the mobile station 44 regarding the
picocell 32.
[0025] Once measurements from the picocell 32 indicate that the
mobile station 44 obtains a sufficient signal from the PCBSU 30,
the radio network controller initiates a handover from the
macrocell 24 to the picocell 32. After successful handover, the
mobile station 44 in one example updates the stored locating
neighbor list 52 and measurements 54 while the mobile station 44 is
in the picocell 32. Periodically updating the locating list 52 and
the measurements 54 allows for accommodating changes that may have
occurred in the macrocellular configuration or the picocellular
configuration of the surrounding area in the vicinity of the
picocell 32. This example technique allows for adapting to network
changes such as the addition of a new base station in the area.
[0026] The disclosed example provides a technique for a mobile
station to determine when it enters a communication range of a
selected picocell. The task of identifying when that occurs, which
corresponds to the mobile station requiring a modified neighbor
list that includes the PCBSU of a selected picocell, is assigned to
the mobile station. This de-centralized approach relieves any
burden from the network side such that specialized neighbor lists
need not be handled by the radio network controller of the
macrocell network. Instead, the mobile station 44 attempts to
correlate a currently received neighbor list with the locating
neighbor list. The mobile station 44 only needs to search for the
PCBSU of a selected picocell when the probability of success for
locating that picocell is high. This is based upon a sufficient
correspondence between the current neighbor list 64 and the stored
locating neighbor list 52. Searching for a particular PCBSU only
when there is a likelihood of finding it saves battery power for
the mobile station.
[0027] One advantage to the disclosed example is that it allows for
mobile stations to use a stored locating neighbor list and
measurement results to identify when the mobile station is in
proximity to a selected picocell. The disclosed example provides a
robust picocell area detection even when an overall network
configuration changes. Because the disclosed example delegates the
task of identifying proximity to a selected picocell to a mobile
station, it provides cost savings by reducing complexity and
signaling overhead on the network side. Additionally, by limiting
the amount of time a mobile station spends searching for a
particular picocell, power consumption is reduced and battery life
is increased. Another advantage to the disclosed example is that it
reduces the likelihood of incorrect picocell identifications, which
may otherwise occur because of cell code re-use, for example.
[0028] The preceding description is exemplary rather than limiting
in nature. Variations and modifications to the disclosed examples
may become apparent to those skilled in the art that do not
necessarily depart from the essence of this invention. The scope of
legal protection given to this invention can only be determined by
studying the following claims.
* * * * *